Process for improving tensile strength of fabric materials



Patented Jan. 22, 1929.

UNITED STATES PATENT OFFICE.

PAUL 1B. COCHBAN, OF WILKINSBUBG, PENN BYLVANIA, ASSIGNOB T WESTINGHOUSE ELECTRIC & MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA.

PROCESS FOR IMPROVING TENSILE STRENGTH OF FABRIC MATERIAL S.

In Drawing.

This invention relates to vegetable fibers havin a high tensile strength and to processes' or increasing the tensile strength of such fibers either before or after they have 5 bfJSIWOVBII or spun into fabric or other materi I One of the objects of the invention is to increase the efliciency of cotton tape used for insulating purposes. Insulation for electric conductors is usually made from fibrous material and it is essential that the insulation be strong, for, if it becomes broken, the conductors carrying electric current will become 'exposed'and considerable danger may result.

My invention, however is not limited to increasing the tensile strength of insulating material alone but relates broadly to the proc ess of increasing the tensile strength of vegetable fibrous materials of all kinds and for 2 whatever purpose used. In fabricating looms, for example, considerable difliculty is sometimes experienced by threads breaking in the looms during the process, and expensive loss results from the consequent necessity of stopping the operation of the looms while the broken threads are bein repaired.

Other ob'ects and advantages of the invention wi appear as the description proceeds.

In experimenting with cotton tape used for insulating purposes, I have made the discovery that, if it is exposed to ozonized air at an elevated temperatulean increase in the tensile strength of the cotton fabric will result.

While the exact nature of the reaction between the vegetable fibers and ozonized air is not known, a chemical reaction probably takes lace. The activity of the ozone may be exp ained b its tendency to break down at 40 or above or inary temperature, forming atomic or ionic oxygen in the nascent state. I do not, however, desire to limit myself to any particular theory that now prevails or may be later developed. A full disclosure of my 5 experiments along this line will now be made.

I took a strip of cotton tape .007 inch thick and three-fourths inch wide and placed it in an electric oven of such construction that the 1927. Serial No. 908,138.

temperature of the cotton tape and of a current of air or a mixture of air and ozone assing through the oven could be regulate A current of dry air was first passed through the oven at the rate of seven liters per minute for periods of eight, sixteen and thirty-two hours, and measurements of the tensile strength of the fabric was made at 10 temperature ranges from 110 to 150 centigrade. No increase in the tensile strength of the cotton tape was found; but, on the contrary, its tensile strength was slightly lowered by exposure to the heated air. 0.1 per cent of ozone was then added to the air, and the resulting mixture was again passed through the oven at the same rate of flow for the same periods of time and at the same temperature 66 ranges as when air was used, and the striking discovery was made that the exposure of the fabric to the ozonized air caused an increase in tensile strength of the fabricof from 20 to 30 per cent.

Another sample of tape was next dipped in an oil varnish having a gummy or resinous base, the specific gravity of which was .851, and drained for fifteen minutes in the open air. The tape was then placed in an electrically heated oven and tests were again made,

. first using dry air and then using air to which 0.1 per cent-of ozone ha's'been added, the gas being passed through the oven at the rate of seven liters per minute and for the same pe 0 riods of time as in the previous example. Tests were again made at 10 temperature ranges from 110 to 150 centigrade, and the results showed that, at temperatures from 110 to 130 centigrade, a varnished tape which has been exposed to ozonized air generally has a greater tensile strength than a varnished tape which has been exposed to a current of air at the same temperature.

In making the experiments, a Perkins tensile tester was used, and, in each case, a. blank tensile strength test was made of the fabric before it was subjected to either the air or the ozone treatment, as it has been found that, frequently, there are variations in the tensile strength of different rolls of cotton tape.

The results of the above experiments are tabulated below:

Tensile strength tests. lBreak-pounds per square inch.]

Air bake Ozone bake Unver- Var- Unvar- Varnished nished nished nished Time tape tape The tape tape Blank 49 Blank 53 8 hours 48 76 8 hours. 61 84 16 hours 47 16 hours 64 93 32 hours 98 32 hours 62 100 .m Q 120 C Blank. 49 Blank 63 8 hours 48 79 8 hours 63 84 16 hours-- 45 88 16 hours 58 101 32 hours 43 32 hours 56 108 Blan 49 Blank 54 8 hours--.-..-- 48 94 8 hours. 59 99 16 hours. 45 103 16 hours. 54 101 32 hours 43 102 32 hour 50 109 Bl ml: 49 Blank. e 49 8 40 96 8 hours. 50 87 16 45 99 16 hours. 42. 89 32 hours 40 97 32 hours 34 87 Blan 4s Blan I 4 8 8 hours. 40 82 8 hours. 46 84 16 hours--. 36 88 16 hours. 34 89 32 hours.. 77 32 hours..----. 24 87 I v Experiments were also made at lower temperatures, and it was discovered that no increase in tensile strength could be obtained by ozone treatment at roomtemperature. At

temperatures between 75 and centigrade, however, the exposing of the fibrous material to ozonized air caused an increase in the tensile strength. This indicates that some heat is necessary to bring about the reaction and it has'been found that a temperature of above 100 centigrade is advantageous in securing the best results. Other experiments demonstrate that, if the ozone concentration in the air flow is increased, the tensile strength will be increased in amuch shorter time than when a lower concentration is used; for ex ample, when the ozone concentration was increased to- 0.5 per cent, the tensile strength of unvarnished cotton tape was increased over 20 per cent in one-half hour at 110" centigrade. If the temperature is increased, the ozone concentration may be decreased and the same results may be obtained; for instance, an increase of 20 percent in the tensile strength of unvarnished cotton tape maybe obtained in one-half hour with an ozone con- Seine cord and it was found that, under proper treatment, an increase in tensile strength of from 20 to 25 per cent was obtained in the wrapping twine and an increase of about 23 per cent was obtained in the cord. If desired, the twine or thread, or even the cotton tape, may be drawn slowly through the oven in a manner well known in the art, it

only being necessary that the temperature of the fibrous material and the ozonized air be such that the desired reaction will take place at the proper ozone concentration. It will be understood that the term oven, as used in the present specification and claims, includes not only an electrically heated oven but any kind of a container or receptacle heated by electric or other means of such nature that the fibrous material and ozonized air may be maintained at the proper temperature.

The term elevated temperature, as used in the present specification and claims, means any temperature above room temperature and below the temperature at which the fibrous material begins to decompose.

In summarizing the results of the experiments on fibrous materials given above, it

' will be observed from the description and from the tables that three factors enter into the results; namely, temperature, ozone concentration and time,'and these factors also vary with varnished and unvarnished fibrous materials.

While numerous examplw have been given and I have described my method in considerable detail, I desire it to be understood that I do not limit myself to the exact examples glven, but wish to claim broadly the idea of increasing the tensile strength of fibrous maexposing them to ozonized air at an terials by elevated temperature;

I claini as my invention:

1. 'The process of increasing the tensile strength 0 vegetable fibrous material which comprises exposing the fibrous material to ozonized air at an elevated temperature. a 2. The process of increasing the tensile strength of vegetable fibrous material which comprises exposing the fibrous material to ozonized air at such temperature that a reaction occurs between the vegetable fibrous material and the ozonized air. 7

3. The recess of increasing the, tensile strength 0 vegetable fibrous materialwhich comprises placing vegetable fibrous material in an oven, passing ozonized air through the oven so that it will come in contact with the fibrous material and regulating the'heat of the oven so that the ozonized air and vegetable fibrous material will be maintained at an elevated temperature.

4. The process of increasing the tensile strength of vegetable fibrous material which comprises dipping vegetable fibrous material in an oil varnish, draining the varnished material in the open air, and exposing the coated product to ozonized air at an elevated temperature.

5. The process of increasing the tensile strength of vegetable fibrous material which comprises placing the fibrous material in an oven, exposing the fibrous material to ozonized air, and regulating the heat of the oven so that the fibrous material and ozonized air will have a temperature between 75 and 110 centigrade.

6. The process of increasing the tensile strength of vegetable fibrous material which comprises placing the fibrous material in an oven, exposing the fibrous material to ozonized air for a period of not more than eight hours and regulating the heat of the oven so that the fibrous material and ozonized air will have a temperature of not above 120 centigrade.

7. The process of increasing the tensile strength of varnished vegetable fibrous material which comprises placing the said material in an oven, exposing the same to'ozonized air for a period of not more than thirtytwo hours and regulating the heat of the oven so that the ozonized air will have a temperature of not above 130 centi ade.

8. The process of increasmg the tensile strength of vegetable fibrous material which comprises exposing it to ozonized air for a period of about thirty minutes at a temperature of not above 150 C., the percentage of ozone in the air being about 0.1 per cent.

9. The process of increasing the tensile strength of vegetable fibrous material which comprises exposing itto ozonized air for a period of about thirty minutes at a temperature of 110 (1., the percentage of ozone in the air being not more than 0.5.

10. Vegetable fibrous material which has been exposed to ozonized air at an elevated temperature and being characterized by having a greater tensile strength than untreated fibrous material of the same character 11. A vegetable fibrous product resulting from the reaction of vegetable fibers and ozonized air at an elevated temperature.

12. A vegetable fibrous product resulting from the reaction of vegetable fibers and ozonized air at an elevated temperature and having 20 to 30 per cent greater tensile strength than the untreated vegetable fibers.

13. A varnished vegetable fibrous product resulting from the reaction of varnished vegetable fibrous material and ozonized air.

14. The process of increasing the tensile strength of vegetable fibrous material which comprises exposing the said material to ozonized air at a temperature between 75 and 150 Centigrade. y

In testimony whereof, I have hereunto subscribed my name this 12th day of July, 1927.

PAUL B. CO CHRAN. 

